27 авг. 2019 г., в 15:25, Vladimir Davydov <vdavydov.dev@gmail.com> написал(а):

On Tue, Aug 27, 2019 at 03:10:47PM +0300, Serge Petrenko wrote:

27 авг. 2019 г., в 15:04, Vladimir Davydov <vdavydov.dev@gmail.com> написал(а):

On Tue, Aug 27, 2019 at 02:22:09PM +0300, Serge Petrenko wrote:
This problem is similar to the one fixed in commit
3c6c1cc96a1a510493c21c472565d4063e403ba2 (lua:fix decimal comparison
with nil)
We should handle box.NULL the same way.

Closes #4454
---
https://github.com/tarantool/tarantool/issues/4454
https://github.com/tarantool/tarantool/tree/sp/gh-4454-decimal-cmp-null

src/lua/decimal.c         |  3 ++-
test/app/decimal.result   | 30 ++++++++++++++++++++++++++++++
test/app/decimal.test.lua |  8 ++++++++
3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/src/lua/decimal.c b/src/lua/decimal.c
index 23e50ba68..8905a0b9d 100644
--- a/src/lua/decimal.c
+++ b/src/lua/decimal.c
@@ -235,7 +235,8 @@ static int
ldecimal_eq(struct lua_State *L)
{
assert(lua_gettop(L) == 2);
- if (lua_isnil(L, 1) || lua_isnil(L, 2)) {
+ if (lua_isnil(L, 1) || lua_isnil(L, 2) ||
+     luaL_isnull(L, 1) || luaL_isnull(L, 2)) {
lua_pushboolean(L, false);
return 1;
}
diff --git a/test/app/decimal.result b/test/app/decimal.result
index 8251e13d8..90d0984b0 100644
--- a/test/app/decimal.result
+++ b/test/app/decimal.result
@@ -248,6 +248,36 @@ a <= nil
| ---
| - error: '[string "return a <= nil "]:1: attempt to compare decimal with nil'
| ...
+-- and with box.NULL
+--
+a == box.NULL
+ | ---
+ | - false
+ | ...
+a ~= box.NULL
+ | ---
+ | - true
+ | ...
+a > box.NULL
+ | ---
+ | - error: '[string "return a > box.NULL "]:1: expected decimal, number or string as
+ |     1 argument'
+ | ...

1 argument?

1st argument


+a < box.NULL
+ | ---
+ | - error: '[string "return a < box.NULL "]:1: expected decimal, number or string as
+ |     2 argument'
+ | ...

2 argument?

2nd argument

But in both cases box.NULL is the second argument, isn't it?

Anyway, looks like it's a different issue, because I get the same
confusing error message while trying to compare a decimal with, say,
a string. We can fix it in a separate patch if we need to.

Ah, I see. Sorry for the misunderstanding.
Yes, here’s the reason for it:
(an extract from https://www.lua.org/manual/5.1/manual.html)
`a >= b is equivalent to b <= a. Note that, in the absence of a "le" metamethod, Lua tries the "lt", assuming that a <= b is equivalent to not (b < a).`
`a > b is equivalent to b < a.`

So, a > box.NULL actually calls `decimal_lt(box.NULL, a)`. That’s why argument numbers get messed up.
AFAIR you don’t have `__gt` and `__ge` metamethods in lua. I guess we should just get rid of argument numbers,
in error messages here, because I don’t see how this can be fixed otherwise.


Pushed the patch to the master branch as is.

Thanks!


--
Serge Petrenko
sergepetrenko@tarantool.org